Embedded EIA-608 captions, from the cloud
The embedded caption format US broadcast runs on, written into your stream by SyncWords with no hardware encoder and no transcoding.
- MPEG-TS over SRT
- RTMP(S) to social
- CC1-CC4 channel control
- 608 passthrough
Where it rides
Two paths carry embedded 608
Embedded 608 is an MPEG transport stream capability. It rides the SRT path into broadcast chains and the RTMP(S) path to social destinations. It is not an HLS feature: for HLS, the player-side answer is WebVTT.
SRT / MPEG-TS
Captions written into the video of your transport stream before the transcoder, alongside any existing 608 passed through untouched.
RTMP(S)
Captions embedded in the stream and rendered natively by YouTube Live, LinkedIn Live and Facebook Live, with nothing to configure at the far end.
Your existing caption encoder
SyncWords also drives Evertz and Link Electronics caption encoders over TCP/TLS, so a plant that already owns 608 hardware migrates to the cloud path at its own pace.
Your own captioner in
Captions from your captioner or steno software are ingested over a direct EIA-608 Control-A connection and carried the same way as AI captions.
Presentation control
The controls engineers actually ask about
Embedded 608 output is not take-it-or-leave-it. Placement and shape are configurable per service and stay attached to it between runs.
- Caption channel
- CC1 through CC4, so language pairs land on the channels your distribution expects.
- Roll-up size
- Two to four lines, with row placement from row 2 to row 15 to keep captions clear of graphics and tickers.
- Line length
- Maximum line length from 20 to 32 characters.
- Passthrough
- Existing 608 in the source is passed through untouched, so upstream captioning survives alongside added languages.
- Languages
- The seven languages the standard supports, including English, Spanish, French, Portuguese and Italian. Other scripts belong in a subtitle track instead.
Frequently asked questions
Can SyncWords deliver embedded 608 inside HLS?
No. Embedded 608 is an MPEG-TS capability, not an HLS one, and SyncWords does not write HLS segments carrying embedded 608. A distribution that needs 608 in HLS can take 608 in SRT from SyncWords and transcode in its own pipeline. Player-side, WebVTT is the HLS-native equivalent.
What about CEA-708?
708 is the digital standard that carries 608 within it, and downstream systems that expect 708 receive what they expect. The practical limits that matter, character sets and languages, are the 608 limits described here.
Can 608 carry Russian, Arabic or Chinese?
Not natively; the standard supports seven languages. Romanized 608 output via transliteration is technically possible, though in practice every customer with those languages chooses a real subtitle track instead: DVB-SUB or DVB-TTML in a broadcast chain, WebVTT player-side.
How quickly do embedded captions land?
Sub-2s caption delay in SRT, where typical captioning solutions display live captions within 4 to 8 seconds. With a few seconds of configurable buffer, captions land with no perceptible delay. The distinction between latency, processing time and delay is on the latency page.
Does this satisfy our FCC caption obligations?
It gives you the output side of the job: captions built to the FCC Title V criteria for accuracy, synchrony, completeness and placement, in the format your distributors ask for. Compliance itself rests with the broadcaster; our output is built to support it.
See 608 on your own stream
Our engineers will embed live captions in a test feed from your chain, so you can check placement, channels and timing yourself.